High-density recording technology for magnetic disk devices has made significant progress in recent years, including remarkable advances in the miniaturization of the magnetic poles included with the magnetic recording heads. However, since a correlation between the strength of the recording magnetic field generated by the magnetic recording head and the volume of the magnetic pole exists, a problem arises in that increased miniaturization of the magnetic pole makes it more difficult to maintain the strength of the recording magnetic field.
Thermally-assisted recording has been developed as one way of dealing with this problem. Thermally-assisted recording works by heating the magnetic recording medium as recording takes place to reduce the coercive field strength, and is a method of recording which reduces the magnetic field strength required for writing. Moreover, more recently a microwave-assisted recording system has been proposed as another form of assisted recording which uses spin torque to enable recording densities greater than 1 Tb/in2. With this system, a high-speed magnetized rotor which rotates at high speed is positioned adjacent to the main magnetic pole of a perpendicular magnetic recording head, with microwaves being radiated onto the magnetic recording medium, recording data on a magnetic recording medium, which has large magnetic anisotropy. Application to the medium of microwaves generated by an oscillator means that the magnetic field required for magnetic reversal in the medium is reduced. This indicates that the strength of the recording magnetic field generated by the main magnetic pole of the magnetic recording head can be less than that required in other conventional devices not using microwaves.
Moreover, as cited both in U.S. Pat. No. 7,443,625 and Tagawa Kanai et al., SRC 27th Technical Report Materials, May 2009, the shingled recording system has been proposed as another high-density recording system. With the shingled system, the tracks recorded in the magnetic recording medium by the magnetic head are partially overlapped. This enables a magnetic recording device to have a track pitch smaller than the tracks recorded. It is also considered possible to use a perpendicular magnetic recording device in which the width of the magnetic pole of the recording head is wider than in conventional devices.
In light of the above situation, it would be beneficial to have a magnetic head that can produce a sufficient recording magnetic field strength while being operated in recently developed systems, such as microwave-assisted recording systems and shingled recording systems.